Chirality: Learning to Control Right- and Left-Handed Molecules, and Understanding Mirror Images

An international team of researchers from Fritz Haber Institut of the Max Planck Society and the Prokhorov General Physics Institute of the Russian Academy of Sciences has discovered a strategy to address molecules that come in opposite or different shapes.

As indicated in a Phys.org report, chirality, which is not an oddity in the world of molecules, is nonetheless a special property.

Meaning, if a molecule is chiral, which is derived from the Greek word, chiros, equivalent to hands, it is existing in two mirrored versions that are quite similar although not identical, like two hands that can be folded together but cannot be positioned congruently on top of each other.

This is the reason experts in the field speak of right-handed and left-handed molecules, or enantiomers, which is the Greek term for "opposite shape."

Chiral Molecules

Essentially, since chiral molecules are very much akin to each other, researchers said there is a real challenge. According to the head of the Controlled Molecules group Dr. Sandra Eibenberger-Arias, from the Fritz-Haber-Institut, the trick is to expose the molecules to electromagnetic radiation in a way that just a single hand, for example, one enantiomer, responds.

This enables them to specifically control right- or left-handed molecules, and find out more about them. Learning this is essential as enantiomers, at times, have very different chemical and biological qualities for which explanations are sought.

Take, for instance, the chiral molecule carvone-one hand is smelling like mint and the other, like caraway. Or the notorious "sedative thalidomide" which is named after its active ingredient," a chiral molecule.

While one form has the intended sedative effect, the other results in birth defects. In their study published in the Physical Review Letters journal, the group of Eibenberger-Arias examined the physical properties of chiral molecules.

Parity Violation

In a similar report, Space Daily specified that according to Fritz-Haber-Institut's JuHyeon Lee, the first author of the published findings, theory predicts a "small energy difference between the two enantiomers, because of what's called "parity violation. Nevertheless, this has not been demonstrated experimentally thus far.

With an innovative combination of different methods though, the research team has come a little closer to attaining this.

Specifically, they illuminated chiral molecules in the gas phase with microwaves or UV radiation. Consequently, right-handed and left-handed molecules are put into different rotational conditions by changing the microwave radiation.

Furthermore, the scientists have thus attained more control than ever before on which hand is in which rotational condition.

Physical Impacts

For the first time, the study authors have also compared experimental findings with accurate predictions from theory, resulting in an improved understanding of the underlying physical impacts.

While total separation of the enantiomers may not be attained yet using this approach, it is exceptional that they could be controlled very successfully in the first place.

This counters the frequently used over-simplified account that they have identical physical properties. Eibenberger-Arias explained that if this was the case, they would then be able to control the enantiomers with the use of physical methods.

The international group of three female and male researchers has therefore laid a good foundation for follow-up investigations, and probably even for experimental evidence of parity violation. The team said this would be a milestone for a basic study, and all applications in the future, as well.

Related information about chiral molecules is shown on Wondersofchemistry's YouTube video below:

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